Problem: The measurement of polydisperse nanoparticles in the region from 10 nm to 1000 nm in liquid is a challenge. Traditional light scattering methods such as dynamic light scattering (DLS), while being excellent for monodisperse samples, tend to skew results to larger sizes (and numbers). This is particularly important in making real time measurements such as in the study of protein aggregation, viral vaccines and exosomes/microvesicles.

Solution: Nanoparticle Tracking Analysis (NTA) from NanoSight visualizes, measures and characterizes virtually all nanoparticles (10-2000nm). Particle size, concentration, zeta potential and aggregation can all be analyzed while a fluorescence mode provides speciation of suitably-labeled particles. The NanoSight technology provides real time monitoring of the subtle changes in the characteristics of particle populations with all of these analyses uniquely confirmed by visual validation.

From loading the sample into the cell to getting results can take as little as 2-3 minutes, with the ability to run batches of samples under the same conditions and directly compare results.

NTA is a method for direct and real-time visualization and analysis of nanoparticles in liquids. Based on a laser-illuminated microscopy technique, Brownian motion of nanoparticles is analyzed in real-time by a CCD or CMOS camera, each particle is simultaneously but separately visualized and tracked by a dedicated particle tracking image analysis program. The NTA program simultaneously identifies and tracks the center of each particle on a frame-by-frame basis throughout the length of the video—typically 30 seconds. The average distance each particle moves in the image is automatically calculated. From this value the particle diffusion coefficient can be obtained and, knowing the sample temperature and solvent viscosity, the particle hydrodynamic diameter is identified. Because each particle is visualized and analyzed separately, the resulting particle size measurement and size distribution does not suffer from the limitations of being the intensity weighted, z-average distribution from DLS. The ability of NTA to simultaneously measure particle size and particle scatter intensity allows heterogeneous particle mixtures to be resolved and particle concentration can be measured directly; the particle size distribution profile obtained by NTA being a direct number/frequency distribution. Because this is an absolute method, no user calibration is required.

The schematic shows the process of an NTA measurement. Figure 1a shows the particles present in liquid illuminated by the laser. Figure 1b shows the individual tracks of each particle. Finally, figure 1c shows the distribution of the particles under study.

NTA technology has found wide acceptance across multiple fields of application with users in industry and academia, as, to date, NanoSight has installed more than 500 systems worldwide. NTA has also been validated by over 600 third party papers citing results obtained using NanoSight instrumentation. This leadership position in nanoparticle characterization is consolidated further with publication of an ASTM International standard, ASTM E2834, which describes the NTA methodology for detection and analysis of nanoparticles.

For more information, please visit http://www.nanosight.com/